Vocabulary
Term
Magnet
Definition
a material that can create magnetic effects by itself
Electromagnet
Magnets created by electric current flowing in wires. A simple
electromagnet is a coil of wire wrapped around an iron core.
Diamagnetic
A type of matter in which the magnetic fields of individual
electrons cancel out, leaving each atom with zero magnetic
field.
Paramagnetic
A material where the magnetism of electrons in individual
atoms does not cancel completely.
Ferromagnetic
A material (like iron) with very strong magnetic properties.
Magnetic
Declination
The difference between the direction a compass points and the
direction of true north.
16.1 Properties of Magnets
A magnet is a material that can create magnetic effects by itself.
All magnets have two opposite magnetic poles, called the
 north pole and
 south pole
What happens if a magnet is cut in half? (see picture below)
Each half will have its own north and south poles.
Magnets exert forces. Two magnets can either attract or repel.
If two of the same poles face each other, the magnets repel.
If two of the opposite poles face each other, the magnets attract.
Two magnets create a force on each other at a distance much larger than the size of the
magnets. Physicists represent this force by drawing the magnetic field around a magnet.
The magnetic field is a magnetic force that surrounds a magnetic object at all points in
space.
The diagram above represents the magnetic field around a magnet. Notice how the
force/magnetic field lines point away from the magnet’s NORTH pole and toward its
SOUTH pole.
Notice below how the magnetic field lines spread out as they get farther away from the
magnet. If field lines are close together, the force is stronger. If field lines are farther
apart, the force is weaker.
Identify in the picture below where the magnetic field is the strongest.
16.1Check Questions
1. Is it possible to have a south pole without a north pole or a north pole without a
south pole. Explain.
2. Think about what happens to a magnet if it is cut in half to answer the next
question. A student knocked a ceramic permanent magnet off her desk, and it
shattered when it hit the floor. Copy the broken pieces and label the north and
south poles on each one.
3. Two magnetic north poles _____ each other. Two south poles _____ each other.
A north pole and a south pole _____ each other.
4. Magnetic field lines outside a magnet always point away from its _____ pole and
toward its _____ pole.
5. The diagram below shows the magnetic field in a region. The source of the field is
not shown. At which of the labeled points in the diagram below is the magnetic
field the strongest?
16.2 The Source of Magnetism
What are electromagnets?
Magnets created by electric current flowing in wires. A simple electromagnet is a coil of
wire wrapped around an iron core.
Watch: http://videos.howstuffworks.com/hsw/11956-magnetism-electromagnetismvideo.htm
Example of an electromagnet:
The north and south poles of an electromagnet are at each end of the coil. When the
fingers of your right hand curl in the direction of the current, your thumb points toward
the magnet’s north pole. This method is known as the right-hand rule.
What happens if you reverse the direction of current flow in an electromagnet?
You can switch an electromagnet’s north and south pole.
Two ways to make the electromagnet’s field stronger:
1. You can add a second battery to increase the current.
2. You can add more turns of wire around the nail.
Diamagnetic: A type of matter in which the magnetic fields of individual electrons cancel
out, leaving each atom with zero magnetic field.
Paramagnetic: A material where the magnetism of electrons in individual atoms does not
cancel completely.
Ferromagnetic: A material (like iron) with very strong magnetic properties.
How can a permanent magnet be demagnetized?
1. Dropping it on a hard surface.
2. Heating it to very high temperature.
3. Forcing two north poles together.
What is a soft magnet?
A magnetic material that is relatively easily magnetized or demagnetized.
A nail is attracted to a magnet and attracts other nails as well. If the nail is removed from
the magnet, it does not attract other nails because the nail is an example of a soft magnet.
16.2 Check Questions
1. What is the difference between diamagnetic, paramagnetic, and ferromagnetic?
2. What happens to the north and south poles in an electromagnet’s if the direction
of the current is reversed?
3. Describe two ways you could increase the strength of an electromagnet.
4. Which picture below shows the correct location of the north and south poles of
the electromagnet?
5. A permanent magnet attracts a steel pin as shown to the right. The pin has become
a soft magnet. Copy the picture and then use what you know about magnetism to
label the north and south poles of the pin.
16.3 Earth’s magnetic field
What people discovered that some naturally occurring materials have magnetic
properties?
The Greeks
Where is Earth’s magnetic north pole?
The north pole of a compass needle points to Earth’s geographic North because it is a
south magnetic pole. Think about it! A compass needle is a magnet that is free to spin.
The north pole of a compass needle (magnet) will always point towards the south pole of
another magnet.
What is magnetic declination?
The difference between the direction a compass points and the direction of true north.
Earth behaves like a giant electromagnet.
16.3 Check Questions
1. Is Earth’s magnetic north pole at its geographic north pole? Explain.
2. Why does a compass point north?
3. What is magnetic declination?